As discussed in the incorporated document, overfilled arch structures are frequently formed of precast or cast-in-place reinforced concrete and are used in the case of bridges to support one pathway over a second pathway, which can be a waterway, a traffic route, or in the case of other structures, a storage space or the like. The terms “overfilled arch” or “overfilled bridge” will be understood from the teaching of the present disclosure, and in general as used herein, an overfilled bridge or an overfilled arch is a bridge formed of arch elements that rest on the ground or on a foundation and has soil or the like resting thereon and thereabout to support and stabilize the structure and in the case of a bridge provide the surface of the first pathway. The arch form is generally arcuate such as cylindrical in circumferential shape, and in particular a prolate shape; however, other shapes can be used. Examples of overfilled bridges are disclosed in U.S. Pat. Nos. 3,482,406 and 4,458,457, the disclosures of which are incorporated herein by reference.
Prior to the structure disclosed in the incorporated 102,921 document, reinforced concrete overfilled arches were usually constructed by either casting the arch in place or placing precast elements, or a combination of these. As used herein, the term “prior art” will refer to structures prior to the structure disclosed in the incorporated 102,921 document. These arched structures rest on prepared foundations at the bottom of both sides of the arch. The fill material, at the sides of the arch (backfill material) serves to diminish the outward displacements of the structure when the structure is loaded from above. As used herein, the term “soil” is intended to refer to the normal soil, which can be backfill or in situ, located at a site used for a bridge structure, and which would not necessarily otherwise adequately support an arch. The terms “backfill,” and “in situ” will be used to mean such “soil” as well.
Soil is usually not mechanically stiff enough to adequately support bridge structures of interest to this invention. Thus, prior art bridge structures have been constructed to transfer forces associated with the structure to walls of the structure and/or large concrete foundations at the base of the wall. Such walls have to be constructed in a manner that will support such forces and thus have special construction requirements. As will be discussed below, such requirements present drawbacks and disadvantages to such prior art structures.
As discussed in the incorporated 102,921 document, for the prior art structures, the overfilled arches are normally formed such that the foundation level of the arch is at the approximate level of a lower pathway or floor surface of an underground structure over which the arch spans. As discussed in the incorporated document, prior art systems include sides or sidewalls which transfer loads from the top of the arch to foundation. The sides of such prior art arch systems must be sufficiently thick and contain sufficient reinforcement in order to be able to carry these loads and the thereby induced bending moments.
Furthermore, as it is necessary to limit the arch loading and bending actions in the top and sides of prior art overfilled arch systems to an acceptable level, the radius of the arch is in practice restricted. This restriction in arch radius leads to a higher “rise” (vertical dimension between the top of the clearance profile of lower pathway surface and the crown of the arch) in the arch profile than is often desirable for the economical and practical arrangement of the two pathways and formation of the works surrounding and covering the arch. This results in a lost height which can be substantial in some cases.
Beams or slabs, while needing a larger thickness than arches, do not require this “rise” and, therefore, can be used for bridges accommodating a smaller height between the top of the clearance profile of the lower pathway and the top of the upper pathway. Arches, despite their economical advantage, often cannot compete with structures using beams or slabs for this reason especially for larger spans. However, the larger thickness may result in an expensive structure whose precast elements may be difficult, unwieldy and heavy to transport to a building site. Thus, many of the advantages of beam or slab structures may be offset or vitiated.
Furthermore, as discussed in the incorporated document, the foundations for the prior art overfilled arch systems must be substantial in order to carry the arch loading and will require additional excavation at the base of the arch (generally beneath the lower pathway) to enable their construction.
For overfilled arches made of precast construction, the incorporation of the required height of the sides or sidewalls of the arch result either in a tall-standing precast element which is difficult and unwieldy to transport and to place or in the requirement of pedestals.
The system disclosed in the incorporated document solves these problems by having foundation blocks located behind or near the top of the side walls and against which the arch of the structure bears. The arch delivers all or at least most of its support forces into the foundation blocks.
This is an extremely effective system and accomplishes all of the objects set forth for this system in the incorporated document.
However, the effectiveness of this structure can be further enhanced by improving the methods used to erect the structure. Therefore, there is a need for a means and a method for building the structure disclosed in the incorporated document Ser. No. 10/102,921.
While the cast-in-place (cip) mode of constructing an arch system is suitable for many situations due to its economy and speed, there are certain commercial and technical (site) conditions for which a totally precast structure is preferred. Some of these conditions are:                time restrictions for on-site installation;        weather conditions, especially low temperatures;        the absence of shuttering and crew suited/trained for the cip construction procedure;        a need to limit the specialist contractors' duties to supplying (and, perhaps mounting) precast elements, in contrast to providing total contractor's services (and responsibility);        limited clear space, not allowing allowint the use of a shuttering (such as with live train lines at the lower pathway);        special requirements (aesthetic, etc.).        
Therefore, there is a need for a means and a method for building a fully precast overfilled shallow arch structure such as disclosed in the incorporated document.
The precast arch elements in many prior systems are cast on their sides. This requires forms which have walls and also may require special handling of the forms to ensure proper formation of the arch elements. Still further, these elements are generally shipped in the side-on orientation. The elements are then lifted off the transporting vehicle, turned in the air to be oriented in the use orientation (as used herein, the use orientation is an orientation shown in FIG. 1 herein as well as in FIGS. 2A–2C of the incorporated document, and a side-on orientation will have the elements rotated 90° with respect to the orientation shown in these same figures). Side-on formation and shipping has several drawbacks: complicated formwork; special transportation problems; and lifting problems associated with lifting and turning such elements.
Therefore, there is a need for a means and a method for forming and shipping a precast arch element such as disclosed in the incorporated document in a use orientation.
In the case of relatively large overfills, no connection may be required between adjacent arch elements because the overfilled soil spreads the loads on the overfill surface so that no differential displacements between adjacent elements occur. Differential displacements are caused by loads, such as traffic loads, placed only on one arch element, then on the adjacent arch element, and so on. Such deformations may lead to so called deflection cracking (cracks that propagate from the top of the arch element to the pavement surface). Such deformations should be avoided.
For shallow arch applications, shallow overfills are more frequent than high overfills since the shallow arch is preferably used where lost height needs to be minimized. In such a case, with only one or two feet or even only inches of overfill or almost-zero overfill in some situations, the live loads may act on individual elements before being transferred to the next one causing the relative vertical displacements that can be such that the pavement of the system will be cracked due to these relative displacements.
Therefore, there is a need for a means and a method for forming an arch system such as disclosed in the incorporated document in a manner that avoids differential displacements between adjacent arch elements of the system.
Still further, there is a need for a means and a method for forming an arch system such as disclosed in the incorporated document in a manner that avoids differential displacements between adjacent arch elements of the system even in the situation of a shallow, or even a zero, overfill.